Craig,

There are a few things that you apparently don't understand about buying
and selling used cars.

First and foremost, you (as a private party) will never get anything
close to average retail value.  That is what a dealership would ask (and
later discount to make the sale) becvause they have additional overhead
in the form of preparing the car for sale and then the implied warranty
that must be extended by law.

Next, ignore values found at kbb.com.  They are a shill for dealerships
to make more money.  The trade-in values are too low and their retail
values are too high.  Instead, use NADA.com as these are the people that
publish "the books" used by dealers.

Private parties generally get something above the wholesale (aka
"trade-in") value but definitely less than retail.  Referring to nada.com:

http://www.nadaguides.com

Assuming "normal" mileage (which would be 60k miles for a 4 year old
car), NADA says that your car is worth $16,150 wholesale and $18,775
retail, so a reasonable private party sale price would be approximately
$17,000.  Adjust up or down based on mileage and additional options.

Hope that helps.